This invention relates to floating equipment used in cementing operations and to methods of fabricating such equipment. More particularly, this invention relates to an improved floating apparatus that is substantially leakproof.
Typically, after a well for the production of oil and/or gas has been drilled, casing will be lowered into and cemented in the well. The weight of the casing, particularly with deep wells, creates a tremendous amount of stress and strain on the equipment used to lower the casing into the well. In order to minimize that stress, floating equipment, such as, but not limited to, float shoes and/or float collars are used in the casing string. Typical of the float equipment that might be used is the Halliburton Super Seal II float collar, and the Halliburton Super Seal II Float Shoe as shown in Oct. 8, 1993 Halliburton Casing Sales Manual, pp. 1-13 and 1-23 respectively.
The float equipment typically consists of a valve affixed to the outer casing which allows fluid to flow down through the casing but prevents flow in the opposite direction. Because upward flow is obstructed, a portion of the weight of the casing will float or ride on the well fluid thus reducing the amount of weight carried by the equipment lowering the casing into the well. Once the casing is in position, cement is flowed down through the inner diameter of the casing, through the valve and into the annular space between the outer diameter of the casing and the well bore. After the cement job is complete, the valve keeps the cement below and behind the casing string.
The float equipment is typically fabricated by affixing a check valve in an outer sleeve which is adapted to be threaded directly into a casing string. The valve is affixed by filling the annulus between the valve housing and the outer sleeve with a high compressive strength cement to form a cement body portion. Over a period of time, the cement poured between the valve and the outer sleeve shrinks slightly as it cures. The shrinkage can cause a micro-annulus between the cement body portion and the outer sleeve and between the cement body portion and the valve. Fluid flowing through the casing can flow through the micro-annulus thus eroding the cement body portion and causing a leak. The leakage through the micro-annulus will allow the cement used to cement the casing in place to reenter the inner diameter of the casing after the cementing job is completed. The cement must be removed by drilling. The leakage will also allow well fluids to contaminate the cement on the outer diameter of the casing, which affects the integrity of the cement and the cementing job. The present invention minimizes any leakage by sealing the cement body portion thereby preventing fluid from flowing into the micro-annulus.